A bench wall planter for the yard

The last two summers have been spent working on the inside of the house, remodeling the rear addition.  The yard was totally ignored, and now it's time to set that right.  A few months ago, we tore out the short chain-link fence that ran along the north boundary of our property and replaced it with a six ft. cedar fence. Then we installed a pair of 2' x 2' x 6' galvanized troughs and planted some black bamboo in them.  The idea is to grow a screen from the east wind and also block the sight line from the street into the yard and kitchen.

Our yard doesn't have a lot of full sun growing area, so I'd thought about putting in some little raised beds somewhere back in front of the bamboo tanks.  Over a few weeks of mocking up with stakes and boards, we decided to build a big, solid project that would provide some hardscaping, a planting area, and eventually a vertical growing structure for maybe a kiwi vine or something similar.

Basically, it's a 12' x 3'-6" raised bed, 16" high, with 6" thick masonry walls around three sides, and treated timber walls across the back.  The masonry walls will be topped with a 12"-16" wide cap so that it provides a seating surface.  Three or four tall posts across the back will support the timber walls and also provide for a trellis of some design tbd.